DESCRIPTION: This study will investigate the visual perception abilities of 70 individuals with mental retardation, from 7 age groups spanning 5 to 65 years of age. Testing will be conducted with seven classes of stimuli to assess: (1) acuity, (2) contrast sensitivity, (3) color, (4) orientation (texture), (5) binocular depth, (6) motion, and (7) flicker perception. The goal of this research is to develop a common testing paradigm that can be used (a) to evaluate whether individuals with mental retardation have selective impairments in their visual abilities, (b) to ascertain whether subgroups of individuals possess different types or degrees of visual impairments, and to specify developmental trends in visual abilities.